The present disclosure relates to an interlock circuit for closing or opening a power supply line and an image forming apparatus with such an interlock circuit.
An image forming apparatus such as a printer or a copier is provided with a cover which is opened and closed in exchanging a consumable such as a toner cartridge and a cover which is opened and closed in removing a sheet remaining in the apparatus due to the occurrence of a paper jam. If a user touches an electrical component (electrical load) in the apparatus during these operations, the user may burn him/herself or get an electrical shock. Thus, the image forming apparatus is generally provided with an interlock circuit for shutting off a power supply voltage supplied to the electrical load when the cover is opened and conducting the power supply voltage to be supplied to the electrical load when the cover is closed.
Here, when the cover is closed, an interlock switch of the interlock circuit is turned on in conjunction with the closing of the cover to resume the supply of the power supply voltage to the electrical load. At this time, an inrush current may be generated and the electrical load and circuit elements constituting the interlock circuit may be deteriorated or broken.
Accordingly, a technology for suppressing the generation of an inrush current by providing a time constant circuit in the interlock circuit is known as a conventional technology 1.
Further, a technology for suppressing an inrush current flowing into an electrical load by reducing a direct-current voltage to a predetermined value when a switch for switching the supply of the direct-current voltage from a direct-current voltage generation circuit to an electrical load is closed is known as a conventional technology 2.
An interlock switch is configured by a mechanical switch for mechanically detecting the opening and closing of a cover and arranged at a position near the cover in a housing. Thus, when opening the cover, a user can easily recognize the presence of the interlock switch. Therefore, the user can intentionally turn on and off the interlock switch by opening the cover and directly touching the interlock switch.
A time constant circuit accumulates electric charges when the interlock switch is on and discharges the accumulated electric charges when the interlock switch is off. Thus, if the interlock switch is repeatedly turned on and off within a certain period, electric charges are injected into the time constant circuit before the discharge of electric charges accumulated while the time constant circuit is on is completed, whereby accumulated electric charges increase. This may cause an excessive inrush current to flow into an electrical load and circuit elements constituting an interlock circuit and deteriorate and break these components.
As just described, the configuration of the conventional technology 1 for preventing an inrush current by providing the time constant circuit has a problem that an excessive inrush current is generated when the interlock switch is repeatedly turned on and off within a certain period by the user. That is, there is a problem that the time constant circuit provided to prevent an inrush current causes the generation of an excessive inrush current.
Further, in the conventional technology 2, the inrush current is suppressed by reducing the direct-current voltage and a premise configuration is different from that of the present disclosure.
The present disclosure aims to provide an interlock circuit and an image forming apparatus capable of preventing the flow of an excessive inrush current even when a user intentionally opens and closes an interlock switch.